Apparatus for the production of polyurethane plastics



J 13, 1956 E. WEINBRENNER ETAL 3,230,047

APPARATUS FOR THE PRODUCTION OF POLYURETHANE PLASTICS Original Filed May6, 1957 FIG. 7

10 F -br rl-- IN VEN TORS.

ERW/N WEINBRENNER. PETER HOPPE KARL BREER.

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A TTORNEY United States Patent i 3,230,047 APPARATUS FOR THE PRODUCTKON0F POLYURETHANE PLASTICS Erwin Weinbrenner, Opladen, Peter Hoppe,'fioisdorf, and Kari lireer, Cologue-Flittard, Germany, assignors, bymesne assignments, of one-half to Farbenfabriken BayerAlrtiengesellschaft, Leverlrusen, Germany, a corporation of Germany, andone-half to Mobay Chemical Company, Pittsburgh, Pa., a corporation ofDelaware Continuation of application Ser. No. 657,318, May 6, 1957. Thisapplication Nov. 30, 1962, Ser. No. 243,969 Claims priority, applicationGermany, May 11, 1956, F 20,266 2 Claims. (Cl. 23-252) The presentapplication is a continuation of copending patent application Serial No.657,318, filed May 6, 1957, and now abandoned.

This invention relates to a process for making porous and homogeneouspolyurethane plastics and to an apparatus for carrying out this process.

In the manufacture of polyurethane plastics from organic compoundshaving at least two reactive hydrogen atoms and polyisocyanates, it isnecessary to intimately mix the isocyanate and a catalyst with the moreviscous polyester or other organic compound having the reactive hydrogenatoms before any substantial reaction has occurred. If a substantiallyuniform mixture of the more viscous material with the other componentsis not obtained almost instantaneously, the resulting product will lackthe required degree of uniformity. Proper mixing of the components ofthe polyurethane plastic has presented a problem and many attempts havebeen made to provide a suitable mixing apparatus. Probably the mostsuccessful heretofore available mixing apparatus is disclosed in US.Patent 2,764,565, granted to Hoppe et al. This apparatus provides forthe injection of the less viscous materials into the more viscousorganic compound having the reactive hydrogen atoms and under mostcircumstances sufficient mixing is achieved.

Although, as indicated hereinbefore, the Hoppe et al. process andapparatus usually provides suitable mixing for making most polyurethaneplastics, it has been found that in some instances even faster and moreuniform mixing would be advantageous.

It is, therefore, a primary object of the present invention to providean improved process for mixing the components of a polyurethane plastic.Another object is to provide a process for the production of porous andhomogeneous pol mrethane plastics wherein the components are mixed insuch manner as to form a truly homogeneous reactive mixture. Anotherobject of the present invention is to provide a process which results inthe formation of polyurethane plastics having improved uniformity. Afurther object of the invention is to provide an apparatus suitable forcarrying out the new improved process of making polyurethanes. Stillfurther objects will become apparent from the following description withreference to the accompanying diagramrnatical drawing in which FIGURE 1is a vertical sectional view of an apparatus in accordance with thisinvention; and

FIGURES 2 and 3 are sectional views of special arrangements which can beused in the apparatus of the present invention.

In accordance with this invention, generally speaking, the foregoingobjects and others are accomplished by providing a process for mixingthe components of a polyurethane plastic wherein the relatively viscousorganic compound having reactive hydrogen atoms or a prepolymer preparedfrom such a compound is mixed with the other components in two separateand distinct injection steps. In the first injection step, thepolyisocyanate or the cross-linking agent and/or accelerator is (are)in- 3,230,047 Patented Jan. 18, 1966 jected into a stream of the organiccompound having at least two reactive hydrogen atoms or of a prepolymer.In the second injection step, the remaining component(s), i.e.,cross-linking agent and/or accelerator or polyisocyanate, if desiredalong with an additional amount of the organic compound having at leasttwo reactive hydrogen atoms, is (are) injected into the mixture obtainedin the first injection step. Stated somewhat differently, the presentinvention contemplates an apparatus and process in which two mixingzones are used and in which mixing is brought about by injection of oneor more components into the other(s), the first of said mixing Zonesserving to mix the organic compound containing at least two reactivehydrogen atoms with part of the other reactants, and the second mixingzone serving to complete the formation of the reactive,polyurethane-forming mixture by adding the residual components to themixture obtained in the first mixing zone. It has been found, inaccordance with this invention, that the mixing of the polyurethanecomponents by injecting the less viscous materials into the more viscouspolyester or similar compound is further improved by injecting only someof the less viscous materials in one step and then injecting the othermaterials in a second step.

In both injection zones, the injection is effected by means of suitableinjection means, such as injection nozzles, through which the componentsare introduced at a pressure substantially higher than that in saidmixing Zones. In general, the injection pressure Will range from about300 p.s.i. to about 15,000 p.s.i., but lower or higher injectionpressures may be used, if desired.

Although the process of the invention is applicable to the production ofporous and homogeneous polyurethane plastics, it is particularly usefulin the manufacture of porous or cellular polyurethane plastics wherecomponents of widely different viscosities have to be brought togetherand intimate and efiicient mixing is of critical importance.

In carrying out the process of the invention, the known formulations formaking polyurethane plastics are employed. Thus, when makingpolyurethane foam, there are ordinarily used 0.6 to 10 mols of organicdiisocyanate per one gram equivalent of reactive hydrogen contained inthe organic compound having at least two reactive hydrogen atoms. Water,accelerator and emulsifier are employed in amounts of 0.5 to 5% byweight, 0.1 to 5% by weight and 0.5 to 10% by weight, respectively,based on the weight of the organic compound having at least two reactivehydrogen atoms. Whereas substantially linear compounds containing tworeactive hydrogen atoms will react with diisocyanates to form elasticfoams, rigid foams are obtained if a dior tri-isocyanate is reacted witha branched compound having three or more reactive hydrogen atoms.

Representative examples of organic compounds having at least tworeactive hydrogen atoms which are commonly used in the production ofpolyurethane plastics include polyesters of the alkyd type, polyalkyleneether glycols and hydrogenation products of olefine-carbon monoxidecopolymers which all contain terminal hydroxyl groups and have molecularweights within the range of about 500 to 10,000. Among the commonlyemployed polyisocyanates are the phenylene diisocyanates, the toluylenediisocyanates, p,p-diphenylmethane diisocyanate and the naphthylenediisocyanates. Cross-linking agents which are frequently utilized in theproduction of polyurethane plastics include water, glycols and diamines,while as examples of accelerators there may be mentioned tertiary aminesand heavy metal compounds. In many cases, emulsifiers, such as highmolecular alkyl sulfates or sulfonatcs, amine salts of high molecularfatty acids, and high molecular alkoxylation products of suitablehydroxyl compounds, are included in the formulation in order tofacilitate mixing of the reactants.

The liquid reaction mixture obtained by the two-step injection procedureof the present invention forms the desired polyurethane plastic whenallowed to stand or heated under the conditions known in the art.

A rather substantial volume of literature has developed in the last tenyears or so in connection with the production of polyurethane plastics.Among the earliest publications are a book entitled, German PlasticsPractice, by De Bell et a1. (1946), pages 316 and 463 to 465, and thearticles by Otto Bayer in Angew. Chemie, A 59, 257 (1947) and ModernPlastics 24, 149 (1947). However, in order to provide sufiicientdetail'with respect to specific starting materials that are especiallyuseful to make polyurethane foam and rubber and at the same time achievea certain degree of brevity herein, reference is made to U.S. Patents2,620,516, 2,621,166, 2,729,618, 2,778,810, and 2,764,565 and to GermanPatent 929,507, the disclosure of which is hereby incorporated herein byreference.

To carry out the process of the invention, an apparatus is employedwhich comprises in combination, a mixing chamber, means for introducinginto said mixing chamber a continuous stream of the organic compoundhaving at least two reactive hydrogen atoms or of a prepolymer, meanslocated adjacent to said continuous stream for injection under pressureinto the mixing chamber and into said stream measured amounts of thepolyisocyanate or cross-linking agent and/or accelerator, a mixing head,pumping means to convey the mixture obtained in the mixing chamber tothe mixing head, means for injection into the mixing head and into themixture measured amounts of the cross-linking agent and/or acceleratoror the polyisocyanate and discharging means for discharging thereactive, polyurethane-forming mixture obtained in the mixing head intoa zone where conversion of the mixture into a polyurethane plastic takesplace.

One embodiment of an apparatus for carrying out the process of theinvention is shown diagrammatically in the drawing. Referring moreparticularly to the drawing, the apparatus illustrated in FIGURE 1includes the container 7 for the organic compound containing at leasttwo reactive hydrogen atoms, the container 1 for the second component,for example, the polyisocyanate or the cross-linking agent and/ oraccelerator and the container 11 for the remaining component-(s), forexample, the accelerator and/or cross-linking agent or thepolyisocyanate.

The mixing chamber 4 is supplied continuously with the compoundcontaining at least two reactive hydrogen atoms from the storagereservoir 7 which is under pressure, for example, air pressure of 2 atm.gauge. The introduction of measured quantities of the activator mixture(cross-linking agent and accelerator) into the stream of the compoundcontaining at least two reactive hydrogen atoms is effected by aninjection pump 2 into the nozzle space 3 of the mixing chamber 4, whichis in addition provided with a pin-type stirrer 6 mechanically driven bya motor 5. The mixture of the compound containing at least two reactivehydrogen atoms and the activator is conveyed by the initial pressureacting on the reservoir 7 through the pipeline 8 to a gearwheel pump 9and from the latter in measured quantities to the mixing head 10. -Inthe mixing head 10, polyisocyanate delivered from the reservoir 11 bymeans of an injection pump 12 is introduced under pressure into thestream of the mixture. The pipe section between the pump 9 and mixinghead 10, which can be of variable volume depending on the reactionvelocity of the system, is under a pressure of, say 150 atm. gauge,whereas the mixing chamber 4 is only under the initial pressure of, forexample, 2 atm. gauge which is acting on the reservoir 7. This obviatesdiflicult sealing problems.

In order to avoid any dripping from the opening 16 of the mixing head 10during intermittent foaming, two pressure valves 13 and 14, FIG. 2, areprovided in the pipe system between delivery pump 9 and the nozzlemixing head 10, the valve 14 being set at a higher pressure than thevalve 13, for example, the valve 14 may have an opening pressure of 30atm. gauge and the valve 13 an opening pressure of 20 atm. gauge. Inaddition, the valve 14 is preferably designed as a relief valve in orderto draw back any residues of the compound having reactive hydrogen andactivator which may remain between the valve 14 and the outlet 16 fromthe mixing head after the apparatus has been stopped, thereby preventingany dripping. This arrangement of pressure valves is particularlynecessary when a transportable mixing head is used and the pipe 15 is ahigh pressure hose. Due to the use of the pressure valves 13 and 14, thedilation of the hose, which is unavoidable when the apparatus is beingmoved, is maintained at the delivery pressure which rises up to atm.gauge, depending on the viscosity of the polyester-activator mixture andon the differential setting chosen for the valves 13 and 14, even afterthe apparatus has stopped, so that when the apparatus is re-started, themixture formed in mixing chamber 4 flows into the mixing head 10 at thesame time as the polyisocyanate is delivered from the reservoir 11 bymeans of the pump 12. As a result, an accurately measured reactionmixture is immediately obtained in the first fractions of a second afterstarting the machine.

As a further control means for the reliable handling of the mixingdevice of the invention and for the sudden stopping of the apparatuswhen filling molds of a given capacity with foam, the control bar of theinjection pump 12 (FIG. 1 and FIG. 3) comprising, for example, sixcylinders is switched to a delivery capacity of zero by means of thelifting magnet 18, while the pump itself is allowed to continue running.If the introduction of, for example, the polyisocyanate into the mixinghead 10, is effected by only one nozzle, all the cylinders of, forexample, the six-cylinder pump operate on this one nozzle. When stoppingthe pump while maintaining the control bar delivery position for thenecessary amounts of polyisocyanate, at least one piston will be at theworking stroke so that a pressure is maintained in the supply pipe whichis only slightly below the nozzle opening pressure (for example, aresidual pressure of atm. gauge as compared with the opening pressure ofatm. gauge). The result is frequently a leakage from the injectionnozzle which leads to a gradual clogging of the mixing head (10), sincethe mixing chamber is filled with the mixture of compound containingreactive hydrogen and activator when the apparatus stops. If inaccordance with FIG. 3 the control bar 17 of the injection pump 19 isadjusted by the solenoid 18 to zero on stopping the delivery of themixture, while the pump is continuing to run, the pressure behind thenozzle falls in about second to the pressure maintained in the container11 and the danger of clogging due to leakage is avoided.

The following examples illustrate the process of the invention in moredetail.

Example 1 The reservoir 7 contains the following polyester mixture:

50 parts of a polyester consisting of 5 mols of adipic acid, 1 mol ofphthalic anhydride, 8 mols of hexanetriol,

30 parts of a polyester consisting of 1.5 mols of adipic acid, 1 mol ofhexanetriol, 1 mol of butanediol,

20 parts of ethoxylated trimethylol propane. The activator mixtureconsisting of 3 parts of N-diethyl- ,B-phenoxyethylamine and 4 parts ofthe sodium salt of a sulionated castor oil containing 54% of water,which is placed in the container 1, is injected into the above saidpolyester mixture in the mixing chamber 4. The mixture of polyester andactivator is then passed into gear- Wheel pump 9 which leads the mixtureinto the injection space of the mixing head 10. In the reservoir 11there is stored toluene diisocyanate which is injected into the mixtureof polyester and activator by means of an injection pump 12 and thehigh-pressure nozzle positioned in the mixing head 19 in such a mannerthat 85 parts of toluenediisocyanate are applied per 100 parts of themixture of polyester and activator. The final mixture leaves the mixinghead through the outlet 16.

Example 2 The reservoir 7 contains a polyester consisting of mols ofadipic acid, 16 mols of diethylene glycol, 1 mol of trimethylolpropane;the container 1 contains an activator mixture consisting of 3 parts ofbis-diethylaminoethanol-adipate, 0.5 parts of the sodium salt of asulfonated castor oil containing 54% water, 1 part of water, 0.2 part ofhexahydrodimethylaniline, 02 part of paraffin oil.

The reservoir 11 contains toluene diisocyanate. A mixture of polyesterand activator 100 parts of polyester and 6 parts of activator isproduced in the mixing chamber. 36 parts of toluene diisocyanate areinjected into 100 parts each of the aforesaid mixture of polyester andactivator in the mixing head 10.

Example 3 Reservoir 7 contains a flame retarding agent and 9 polyestermixture of the following composition:

80 parts of a polyester consisting of 5 mols of adipic acid, 1 mol ofphthalic anhydride, 8 mols of hexanetriol; parts of a polyesterconsisting of 14 mols of adipic acid, 15 mols of diethylene glycol;parts of trichloroethyl phosphate.

Container 1 contains the following activator mixture:

2 parts of siliceous chalk,

4 parts of the sodium salt of a sulfonated castor oil containing 54%water,

3 parts of perrnethylated triethylenetetramine,

3 parts of N-diethyl-B-phenoxyethylamine,

85 parts of toluene diisocyanate, which are placed in the reservoir 11,are injected into 100 parts each of the mixture of polyester, activatorand flame retarding agent in the mixing head 10.

Example 4 A mixture of polyester and activator is produced in the mixingchamber 4. 90 parts of a polyester consisting of 15 mols of adipic acid,

16 mols of diethylene glycol,

1 mol of trimethylol propane and 10 parts of a polyester consisting of 1mol of adipic acid,

1 mol of ethylene glycol,

are stored in reservoir 7 and the activator mixture consisting of 4parts of bis-(diethylaminoethanol)-adipate, 1 part of a sodium salt of asulfonated caster oil consisting of 54% Water, 4 parts of water,

is stored in container 1. 48 parts of toluene diisocyanate from thereservoir 11 are injected into 100 parts each of the mixture ofpolyester and activator in the mixing chamber 10.

Example 5 A mixture of polyester and activator consisting of parts of apolyester consisting of 2 mols of adipic acid, 0.5 mol of phthalicanhydride, 3.5 mols of trimethylolpropane, 1 mol of 1,3-butanediol, 20parts of a polyester consisting of 15 mols of adipic acid 16 mols ofdiethylene glycol 1 mol of trimethylol propane and 0.7 part of the ironcomplex salt of cyclopentanonemonocarboxylicacidethylester,

is produced in the mixing chamber 4. The polyester component is passedfrom the reservoir 7 and the activator component from container 1. 44parts of toluene diisocyanate are injected from the reservoir 11 intoparts each of the aforesaid mixture.

The mixing device of the invention is suitable for the measuredintroduction of reaction mixtures into molds or hollow elements of alltypes. The capacity of the apparatus can 'be designed for a deliveryspeed of from 1 to 60 kg./miu., depending on the size of the cavity tobe filled. It is also possible to use the apparatus according to theinvention to supply measured quantities of homogeneous materialscomprising a polyurethane to casting or injection-molding process.

Furthermore, the improved apparatus according to the invention can beused for the production of homogeneous or porous plastics where aninitial reaction product of a polyester or polyether and apolyisocyanate is combined with an activator system to produce the finalreaction mixture. In this case, the polyester or polyether is initiallymixed with the polyisocyanate in the mixing chamber 4 (see FIG. 1) andthe mixing chamber 4 and the pipe '8 are heated, thus the pipe 8 may bea throughflow heater. The activator system is in this case supplied tothe mixing head 10 from the reservoir 11 through the controlledfeed pump12.

While certain representative embodiments and details have been show forthe purpose of illustrating this invention, it will be apparent to thoseskilled in the art that various changes and modifications may be madetherein without departing from the spirit and scope of the invention.

What is claimed is:

1. An apparatus for mixing the components of a polyurethane plasticwhich comprises a first mixing chamber having an agitator disposedtherein, a discharge outlet and at least two inlets at least one ofwhich is a means for injecting under pressure a first component into asecond component, separate supply containers for each of said first andsecond components, a pumping means having a suction side and a dischargeside, a first conduit conmeeting said discharge outlet of said firstmixing chamber to said suction side of said pumping means, a secondmixing chamber having a discharge outlet and a first and second inlet,at least one of which is an injection means for introducing a componentunder pressure, and a sec ond conduit connecting the discharge side ofsaid pumping means with said first inlet of said second mixing chamber,a second pumping means and a third conduit for connecting said secondpumping means with said sec ond inlet of said second mixing chamber.

2. An apparatus for mixing the components of a polyurethane plasticwhich comprises a first mixing chamber having a discharge outlet and atleast two inlets at least one of which is a means for injecting underpressure a first component into a second component, a pumping meanshaving a suction side-and a discharge side, a first conduit connectingsaid discharge outlet of said first mixing chamber to said suction sideof said pumping means, a second mixing chamber having a discharge outletand a first and second inlet, at least one of which is an injectionmeans for introducing a component under pres sure, and a second conduitconnecting the discharge side of said pumping means with said firstinlet of said second mixing chamber, a first pressure sensitive valveand a second pressure sensitive valve disposed in said second conduit,said first pressure sensitive valve located in said second conduitbetween said first pumping means and said References Cited by theExaminer UNITED STATES PATENTS 9/1956 Hoppe et a1 23252 X 1/1957 Reis.

10 MORRIS O. WOLK, Primary Examiner.

JAMES H. TAYMAN. JR.. Examiner.

1. AN APPARATUS FOR MXING THE COMPONENTS OF A POLYURETHANE PLASTIC WHICHCOMPRISES A FIRST MIXING CHAMBER HAVING AN AGITATOR DISPOSED THEREIN, ADISCHARGE OUTLET AND AT LEAST TWO INLETS AT LEAST ONE OF WHICH IS AMEANS FOR INJECTING UNDER PRESSURE A FIRST COMPONENT INTO A SECONDCOMPONENT, SEPARATE SUPPLY CONTAINERS FOR EACH OF SAID FIRST AND SECONDCOMPONENTRS, A PUMPING MEANS HAVING A SUCTION SIDE AND A DISCHARGE SIDE,A FIRST CONDUIT CONNECTING SAID DISCHARGE OUTLET OF SAID FIRST MIXINGCHAMBER TO SAID SUCTION SIDE OF SAID PUMPING MEANS, A SECOND MIXINGCHAMBER HAVING A DISCHARGE OUTLET AND A FIRST AND SECOND INLET, AT LEASTONE OF WHICH IS AN INJECTION MEANS FOR INTRODUCING A COMPONENT UNDERPRESSURE, AND A SECOND CONDUIT CONNECTING THE DISCHARGE SIDE OF SAIDPUMPING MEANS WITH SAID FIRST INLET OF SAID SECOND MXING CHAMBER, ASECOND PUMPING MEANS AND A THIRD CONDUIT FOR CONNECTING SAID SECONDPUMPINGT MEANS WITH SAID SECOND INLET OF SAID SECOND MIXING CHAMBER.